NRC Grants Long Mott Construction Permit in Texas

The US Nuclear Regulatory Commission has issued a construction permit for the Long Mott Generating Station in Calhoun County, Texas, a proposed four-reactor plant at Dow’s Seadrift Operations site. In NRC release No. 26-083, dated 9 November 2026, the agency says the facility is designed around four X-energy Xe-100 reactors and “will primarily generate high-temperature steam for industrial use at the Dow Seadrift Operations site. Excess electricity will be exported to the grid.”

A construction permit is not permission to switch the plant on. The NRC is explicit: the permit “authorizes the company to build the facility but does not authorize operation.” Before fuel is loaded or the reactors are operated, the company must obtain a separate operating licence. Dow’s own announcement is just as plain about the commercial decision: “Receipt of the construction permit does not represent a final decision by Dow to proceed with construction of the proposed facility.” If approved, Dow says, construction could begin later this decade, with startup early next decade.

What the NRC permitted at Long Mott, and which “firsts” it claimed

The permit goes to Long Mott Energy, LLC, which Dow describes as its wholly owned subsidiary, working with X-energy under the US Department of Energy’s Advanced Reactor Demonstration Program. The project is a high-temperature gas-cooled design, intended to replace energy and steam assets at the Seadrift site as they near the end of their life.

The NRC’s “firsts” are specific, and they should be kept that way. It calls this “the first construction permit for a high-temperature gas-cooled reactor in nearly 60 years,” and “the third advanced reactor construction permit the NRC has issued this year.” It also lists “its first approval of a multimodule advanced reactor facility; its first approval of a reactor with a pebble-bed core; its first approval of a design featuring online nuclear refueling; and its first review of a high-temperature gas-cooled reactor under the agency’s risk-informed, technology-inclusive Licensing Modernization Project framework.” Those are the agency’s own, limited claims. They are not a finding that this is the first construction permit the NRC has ever issued for any reactor.

X-energy’s statement and Dow’s go further in places. X-energy describes the proposed four-unit plant as one that “would be the first advanced nuclear facility to power an industrial site in the United States.” Dow says the station “is expected to be the first advanced nuclear project deployed at an industrial site in North America.” Those are company characterisations, not the NRC’s list. X-energy also says each Xe-100 is an 80 MWe / 200 MWt reactor. Neither official release states a project cost.

The same Xe-100 design is already in TSN’s coverage of Amazon, X-energy and AEP’s plan to explore 12 Xe-100 units in Indiana. That Indiana work is a separate proposal. Other recent small-reactor stories, including NuScale’s manufacturing deal with Doosan and Blue Energy’s application to the NRC for a Texas small reactor, sit in the same wider licensing picture without being this permit.

A permit to build is still several decisions short of a plant

Dow lists remaining milestones before any construction, including further engineering and design work and a review by its board. Edward Stones, business vice president, Energy & Climate at Dow, said the company would “continue to evaluate the project through the lens of competitiveness, execution readiness, and capital affordability before any decision regarding construction is made.” X-energy, in its own release, says “Dow is expected to consider a preliminary investment decision in 2027,” and that full-scale nuclear construction would follow a Dow final investment decision. That 2027 date is X-energy’s account of a Dow decision, not an X-energy investment decision of its own.

For a UK or any other reader watching advanced nuclear timetables, the sequence is therefore still conditional: a US construction permit, then a separate operating licence, then a company decision to spend the capital. The NRC says it completed a safety evaluation in October, a month ahead of schedule, and issued an environmental assessment and finding of no significant impact in May. Those reviews support the permit that has been issued. Neither review authorises operation, and neither binds Dow to build.

The next documents that would change the story are an operating-licence application, and a Dow decision — preliminary or final — to proceed. Until then, Long Mott is a permitted design at Seadrift, not a plant under construction.